Consider a function: f(n) = number of elements in the set {a: 0 <= a < n and gcd(a,n) = 1}. What is this function?

Consider a function: f(n) = number of elements in the set {a: 0 <= a <

1.	Consider a function: f(n) = number of elements in the set {a: 0 <= a < n and gcd(a,n) = 1}. What is this function?
A.	Primitive
B.	Totient
C.	Primality
D.	All of the mentioned
Answer» C. Primality